Secret Nuclear Bunker

Secret Nuclear Bunker, Iran is reinforcing its most sensitive nuclear facility against a possible attack, presenting Israel with a closing window of opportunity for a successful air strike, The Daily Telegraph has learned.

The development of the Fordow Fuel Enrichment Plant will alter the calculations of Benjamin Netanyahu, the Israeli prime minister, and President Barack Obama when they meet on Monday.

Wary of the risks of war, Mr Obama is expected to argue that sanctions and diplomatic pressure should be given more time to compel Iran’s leaders to reassess their nuclear ambitions.

But Mr Netanyahu must weigh the probability of Israel losing any independent military option when the Fordow plant is finished. This previously secret facility, dug into a mountainside in the Great Salt Desert, is a nerve centre of Iran’s nuclear program: 696 centrifuges for enriching uranium are in place beneath layers of rock and earth, believed to be some 260ft (80m) deep.

When complete, Fordow could be invulnerable to the GBU-28, the heaviest “bunker busting” bomb in the arsenal of Israel’s air force. Ehud Barak, the Israeli defence minister, has said that Iran would then be able to concentrate its nuclear capability inside a “zone of immunity”.

But that moment has not yet arrived. An official from a country in the region said that Iran was working to “harden” Fordow against attack. Despite its mountainside location, the plant is believed to have points of vulnerability, including entrances and ventilation shafts.

More work is believed to be under way to minimise any such weaknesses. Until then, the official added that an Israeli attack might still succeed in disabling Fordow, but the option could disappear when the hardening process is complete.